Velocity measurements in the nip region of a co-rotating twin-screw extruder using laser Doppler anemometry

The laser Doppler anemometer (LDA) technique has been successfully applied to measure the local velocities in the nip region of a twin-screw extruder. Tangential and axial components of velocity for heavy corn syrup were measured below and on either side of the nip. The experimental data show that the flow in the nip region is asymmetric and highly three dimensional. Highest velocity gradients were observed below the nip, and the maximum tangential velocity occurred 2 to 3 mm below the nip. Leakage flow between flights was also detected.